2017 Volume 59 Issue 10 Pages 2521-2525
During a secondary screening visit by an 81-year-old man at our hospital, we detected a 5-mm flat elevated lesion in the rectum while performing total colonoscopy. The lesion consisted of a white, flat, elevated portion and a reddened protruding portion. On magnified endoscopy, the white, flat, elevated portion showed a type Ⅱ pit pattern and the reddened protruding portion showed a type ⅢL pit pattern. To assess the possibilities of a partial change in the serrated lesion or the development of a collision tumor in the serrated lesion along with adenoma, endoscopic mucosal resection was performed. Pathological examination determined that the flat elevated portion was a hyperplastic polyp and that the protruding portion was tubular adenoma. Molecular biological analysis indicated a K-ras mutation only in the white flat elevated portion, and neither a K-ras mutation nor a BRAF mutation was observed in the reddened protruding portion. The findings on endoscopy, pathology, and molecular biology analysis indicated that the growth was a collision tumor of a hyperplastic polyp and tubular adenoma.
